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What made Chelsea's defeat all the more galling was that Mourinho selected a side that suggested his priority was Thursday's decisive Europa League quarter-final tie at home to Anderlecht, which remains United's best route of re-entry to the Champions League, even after this huge victory.

Top scorer Zlatan Ibrahimovic started on the bench, along with midfield anchorman Michael Carrick and playmaker Henrikh Mkhitaryan, as Mourinho selected a curious line-up, but one whose collective zeal and desire proved too much for Antonio Conte's insipid side.

Marcus Rashford and Jesse Lingard led the line in the absence of Ibrahahimovic, Chelsea's usually well-drilled defence unable to handle their pace and movement, as Mourinho's faith in youth and tactical boldness was vindicated.

Rashford scored the opener and earned a standing ovation for his contribution when he was replaced late on, while Lingard's job was done just after the hour mark, his intelligent running and link-up play having helped United a establish a two-goal lead they would not relinquish.

Mourinho played with a three-man defence, with Ashley Young and Antonio Valencia deployed as wing-backs to ensure their opposite numbers were pushed back, while Ander Herrera and Matteo Darmian were detailed to man-mark Eden Hazard and Pedro respectively.

(Image: Action Images via Reuters)

It was a tactical masterclass from Mourinho, with Hazard in particular subdued throughout, the normally ebullient Chelsea playmaker stalked by Herrera throughout and needing a restraining order to shake him off by the final whistle.

Mourinho had claimed there was no emotion involved in facing his former club, particularly after suffering two chastening defeats at their hands already this season, but the way he paced his technical area throughout suggested otherwise.

There was a degree of fortune about United's opener in the seventh minute, Herrera clearly handling the ball as Nemanja Matic tried to thread a ball through to Chelsea's attackers, referee Robert Madley failing to spot the transgression which proved costly for the visitors.

Herrera produced a sublime pass behind the Chelsea defence, Rashford timed his run to perfection and out-paced David Luiz before steering an angled shot beyond Asmir Begovic, in goal for the injured Thibaut Courtois.

United never took their foot off the gas, never allowing Chelsea to settle into any kind of rhythm, snapping into tackles and playing with a swagger that must make Mourinho wonder why they have succumbed to so many draws at home this season that have undermined their progress.

(Image: 2017 Getty Images)

The killer blow came four minutes after the restart, Young showing great tenacity to retrieve the ball, his determination eventually seeing it spill to Herrera, whose fierce shot took a deflection off Kurt Zouma – called into the side after Marcos Alonso was injured in the warm-up – and past Begovic.

Once United had doubled their lead, there was no way they were going to hand Chelsea a way back, Mourinho tightening their hold on the game by bringing on Carrick and Ibrahimovic to see out the win, Chelsea's resolve broken with a second Premier League defeat in the space of a fortnight.

A 13-point lead a month ago is now down to four, with Tottenham steamrollering opponents and sensing their chance to reel in Conte's side and ensure a thrilling finale to the title race.

The two sides meet at Wembley on Saturday for a place in the FA Cup final, but for Chelsea the priority is ensuring they do not blow a title race they have had in their grasp for some time.

For United and Mourinho in particular, there was satisfaction at putting Chelsea to the sword, and a reminder to the rest of the Premier League that, with the right acquisitions this summer, they are sure to be challenging for the title next season.